Highly active antiretroviral therapy (HAART) dramatically improves the survival of patients with HIV. The effectiveness of HAART in routine care is determined by the success with which patients are able to follow certain crucial Steps of HIV Care, which includes 1) access outpatient care, 2) utilize care and treatment services, and 3) adhere to care. Yet even in the HAART era, about 40% of persons with HIV do not enter care within 6 months after diagnosis, and adherence remains a challenge at all levels. Studies to date have not been able to follow patients through the entire Steps of HIV Care. As a result, we do not have a clear understanding of why patients so poorly engage in care, or the clinical and societal consequences of inadequately following the Steps of HIV Care. This application is for innovative, preparatory services research. Three essential elements are needed to study the Steps of HIV Care: a validated model for the interaction of patient and health care system, validated instruments to measure key constructs, and a methodology to analyze these extremely complex data. We will achieve these elements in the context of a prospective observational cohort study of patients enrolled at the time of HIV diagnosis, followed every 3 months for 18 months. We will accomplish 3 aims: 1) Assess the relation of attitudes and beliefs about HIV disease and care over time and relate those attitudes and beliefs with success in following the Steps of HIV Care. 2) Validate a simple visual analogue scale-based instrument for assessing adherence to HAART in patients newly starting HAART in routine care. 3) Test the robustness of latent growth curve analysis for modeling changes in attitudes and beliefs overtime, and non-recursive causal modeling with longitudinal data analysis techniques for assessing the impact of each component of the Steps of HIV Care model on health outcomes. These studies will allow us to identify modifiable factors for improving outcomes, and target the Step of HIV Care where interventions should be focused to maximize impact.